Seek solutions to cavitation in slurry pumps
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The slurry pumps experience cavitation during operation, producing a popping sound. In less than half a year, two of these pumps required replacement of their pump shafts and impellers. One shaft had a small area of fatigue damage starting from the keyway, along with a broken key; the other shaft also had irregular through-cracks starting from the keyway (visible from the end face of the shaft). Cracks were present on the hub of the impeller, as well as in the balance holes and flange areas. Urgent solutions are needed – I hope experts can provide some guidance. reward_7ree
There are two solutions: 1 is to have the pump manufacturer redesign the pump in order to reduce NPSHr. 2 is to modify the process conditions on-site to increase NPSHa. This is a fundamental solution; temporarily alleviating cavitation can be achieved by reducing the flow rate or the temperature of the medium.
The main cause of cavitation in slurry pumps is insufficient suction volume due to blockage at the inlet, and this blockage may be caused by slag or foreign objects. Solutions: 1. Add a mixer or choose a slurry pump with impeller blades (vertical type). 2. Dilute the pump inlet with flushing water to resolve the problem at the pump inlet.
First, determine whether the damage to the impeller and shaft is caused by cavitation. 1. Does the material meet the requirements specified in the design?； 2. Are the motor and pump powers matched? Excessive shaft power can cause the key to suffer from fatigue damage ； 3. Pressure buildup at the pump outlet, low flow rate, and rising temperature lead to cavitation.
Thank you for your reply. The material of the shaft is 40CR; I’m not sure whether heat treatment was carried out in accordance with the technical requirements. The pipeline may develop scale, resulting in low flow rate; please check it again.
There is a flushing water pipeline, but in my opinion its effectiveness is poor
Use a flushing method similar to that of violent agitation.
That’s a good question. I happen to have some experience that I can share: slurry pumps tend to get clogged, so one solution is to install a water pipe at the inlet, or use a minimum flow tube; increasing the amount of seal water might also help
Given the viscosity of the fluid, try reducing the speed for now. It is best to contact the pump manufacturer to resolve this issue; is the material highly corrosive?
If possible, try pressurizing the inlet
Well, prepare to connect the pump outlet to the inlet pipeline